eZ\Publish\Core\FieldType\Relation\Type::checkValueStructure PHP Метод

    protected function checkValueStructure(BaseValue $value)
    {
        if (!is_integer($value->destinationContentId) && !is_string($value->destinationContentId)) {
            throw new InvalidArgumentType('$value->destinationContentId', 'string|int', $value->destinationContentId);
        }
    }